Telephone-exchange system



Jan. 8, 1924,

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Patented Jan. 8, 1924.

UNITED STATES PATENT OFFICE.

JACOB W. LATTIG, OF BETHLEHEM, PENNSYLVANIA, ANI) CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCH ANGIE SYSTEM.

Application filed March 16, 1922.

To all whom it may concern:

Be it known that we, JACOB W. LATTIG and CHARLEs L. GoooRUM, citizens of the United States, residing at Bethlehem, in

the county of Lehigh, State of Pennsylvania, and New York, in the county of New York,

State of New York, respectively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of

which the following is a full, clear, concise,

and exact description.

This invention relates to telephone systems and more particularly to coin collecting and metering systems for automatic telephone exchanges, being a continuation in part of the application of Lattig and Goodrum, Serial No. 52,512, filed September 24, 1915.

The object of this invention is to automatically charge a subscriber for the service which he requires in accordance with the time consumed in conversation and the nature of the connection which has been established therefor.

According to one feature of this invention, upon the successful establishment of a connection the calling subscribers charging device, which ma be a coin collector or a call register or bot is automatically operated for each time unit during which the conversation is kept up.

According to another feature of this invention, if a call is extended to a reversecharge line, instead of the calling subscribers charging device, the called subscribers charging device is operated at certain intervals during the conversation. By a reverse-charge subscriber, is meant one calls to whom are not charged against the calling but against the called subscriber.

Still another feature of this invention relates to an automatic telephone system in which the rate of the charges made for the time units of the conversation are dependent on the trunk employed for the extension of a call.

Furthermore, this invention contemplates the use of trunk lines of diiferent character- Serial No. 544,091.

istics, as trunk lines of difi'erent length or trunk lines leading to difierent exchanges.

Both local and so-called long distance connections may be established and means are provided for charging the calling subscriber, or the called subscriber in case a connection is established to a reversecharge line, accordingl Means are provided i br charging a subscriber in accordance with any tariff which a telephone company may establish. For instance, the charged subscriber may be charged at one rate for an initial period of conversation, spoken of as the call, and at a different rate for each additional eriod of conversation. In the parlance o telephony a call consists in the establishment of a connection and the holding of a conversation thereover for a specified length of time and a specific charge which varies with the trunk line used is made. For additional periods of conversation a charge ata different rate is made because no new operation of the apparatus is necessary, it being only required to maintain the originally established connection. Thus in one case a charge of ten cents may be made for mean lasting three minutes and a charge of five cents for each additional period of five minutes. In another case a charge may be made of fifteen cents for a call lastin three minutes and a charge of five cents or each additional period of four minutes. In a third case a charge may be made of five cents for a call lasting three minutes and an additional charge of the same amount for each additional period of the same length. Thus the charges may be varied in any desired manner.

In another aspect of this invention the conversation may be interrupted or may be continuous or uninterrupte In the case where coin collectors are used the calling subscriber if he is to be the charged subscriber may not insert a coin into the collector until after the connection is established and the called party has answered. He may do this to assure himself that he has been connected to the right party as when the called subscriber answers, the calling subscribers transmitter is rendered inoperative, but his receiver is not and he ma therefore attem t to recognize the cal ed partys voice befb're making payment. If he does recognize the called partys voice he may insert a coin in the collector whereupon the conversational circuit will be rendered operative. The calling subscriber may insert only so many coins as are required for the call whereupon if the conversation extends beyond the specified time the conversational circuit will be disabled and he will be required to insert an additional coin to pay for an additional period of time and so on. On the other hand, the calling subscriber after recognizing the voice of the called subscriber may insert a plurality of coins so that they may becollected automatically at the beginnin of the call and at the beginning of eac additional period of time. Or a ain, he may insert a plurality of coins be ore establishing the connection in which case there will be no interruption of the conversational circuit at all and the coins will be collected periodicallv and automatically.

ere the calling substation is not equipped with a coin collector the charging is done periodically and automatically as in the case where a plurality of coins are inserted before the establishment of the connection, the charging bein accomplished by meansof the meter mdivi ual to the line.

The drawings com rise in all twenty-two figures. Fig. 17 is a ey chart showing how certain of the fi ures may be placed to form diagrammatic i] ustrations of different kinds of connections which may be established. Figs. 1-, 1 and 1 show diagrammatically three different types of calling substations together with a trunk huntin selector. The trunk hunting selector in eac of these three figures is exactly alike but the substation apparatus is somewhat different. In Fig. 1 the substation apparatus hereinbefore disclosed in the application of Lattig and Goodrum. Serial No. 52,512, filed September 24, 1915, is shown and represents the preferred type of substation and coin collector. Fig. 1 shows a substation which is not equipped with a coin collector and Fig. 1 shows a substation equipped with a coin collector of the general type of that disclosed in the patent to Scribner 728,309, granted May 19, 1903. Fig. 2 diagrammatically represents a first selector with a time control switch for controlling the substation meter and coin collector. Figs. 3 and 3 diagrammatically re resent the apparatus employed in inter- 0 cc trunks at the outgoing end thereof together with time control mechanism for controlling the substation meter and coin collector on interoflice calls. Figs. 4 and 4 diagrammaticall represent the incoming ends of intero ce trunks, each comprising a second selector and a time control mechanism for controllin the called subscribers meter on a reverse service interoflice connection. Figs. 3 and 4 taken together represent one interoflice trunk and Flg. 3 and Fig. 4 taken to ether represent an interoifice trunk of a di erent character such for instance as would connect to a difi'erent distant office or one at a different distance. Fig. 5 diagrammatically represents a third selector and Fig. 6 diagrammatically represents a connector switch. Figs. 7 and 8 are diagrammatic representations of the coin collector employed in Fig. 1, Fig. 7 representing the armature of the coin collector in its neutral or normal position and Fig. 8 representing the armature in its position when actuated to collect a coin. Figs. 9 and 10 are schematic representations of the armature and contact arrangements for the magnet of the coin collector used in connection with Fig. I, Fig. 9 representing the armature rotated in one direction and Fig. 10 representing the armature rotated in the opposite direction. Fig. 11 is a perspec tive view with sections cut away showing the arrangement of the substation magnets and armatures for controlling the disposition of coins in the coin collector used in connection with Fig. 1 Fig. 12 is a top view of the same. Figs. 13, 14 and are diagrammatic representations of the coin chute illustrating the operation of the coin collector, and the path taken by the coins as the armature of the coin collector magnet is actuated. Fig. 13 shows the positions which the coins assume when the magnet retains its armature in its neutral position. Fig. 14 shows the disposition of the coins as the armature of the coin collector magnet is moved to the coin collecting position and Fig. 15 shows the operation of the col lector as the refund magnet is operated. Fig 16 and Fig. 16 are schematic representations of the essential circuit arrangements of the connector switch shown in Fig. 6 when arranged for regular service and for reverse-charge service respectively. Fig. 17 as beforestated is a key chart. This figure shows that by using Figs. 1 2. 3". 4", 5

and 6 (connected as indicated in Fig. 16*) an interoifice connection over a particular interoffice trunk to a regular called substation may be illustrated. This also shows that by using Figs. 1. 2, 3. 4' 5 and 6 (connected as indicated in Fig. 16*) a similar connection employing an interoffice trunk line of different characteristics, such a trunk line for instance as would go to a different exchange or an exchange at a different distance may be illustrated. Taking Figs. 1, 2, 3*, 4, 5 and 6 connected as indicated in Fig. 16, an interoflice reversed service connection is illustrated. With Figs. 1*, 2, 5 and 6 connected as indicated in Fig. 16, an intraofiice connection to a re lar called subscriber is illustrated and wit Figs. 1*, 2, 5 and 6 connected as indicated in Fig. 16 an intraoffice connection to a. reversed service called line is illustrated.

The type of switch used in connection with circuits illustrated in Figs. 1 to 6, inclusive, has been shown and described in the patent to Goodrum No. 1,135,011 to which reference may be had for the purpose of amplifying the following description.

Operation of calling substations.

In Fig. 1 is a diagrammatic representation of one type of substation provided with a coin collector. The substation 100 is connected to the line wires 150, 151. When the receiver is removed from its hook 106 a circuit is established from conductor 150, receiver hook 106, contact 107, winding of polarized relay 103, contact 108, contact 109 to conductor 151. As will hereinafter appear, conductor 150 is connected to ground and conductor 151 is connected to battery. Current flowing through this circuit will energize the polarized relay 103 so as to close contacts 110 and 111. There upon a circuit is closed from conductor 150, receiver hook 106, contact 112, primary winding of induction coil 113, transmitter 114. contacts 110, 111. contacts 108 and 109 to conductor 151. Thus, a low resistance bridge including the transmitter is connected across conductors 150 and 151. The receiver circuit is as follows: contact 107, receiver 105, secondary winding of induction coil 113, condenser 115, contacts 111, 110, transmitter 114, primary winding of induction coil 113, contact 112, receiver 00k 106 to contact 107.

As the receiver hook is moved upwardly when the receiver is taken therefrom the member 116 rides under the back of the contact spring 117 andmoves it to the right so that it does not make connection with contacts 118 and 119. When the receiver is replaced the member 116 rides down on the outer face of the contact spring 117 and moves it to the left whereby connection is made to contacts 118 and 119 completing a connection from ground through the magnet 104, contact spring 117, contact 118 to conductor 150 and through contact spring 117. contact 119, contacts 108 and 109 to conductor 151. The connection of ground simultaneously to both conductors of the line is for the urpose of releasing the connection as will hereinafter appear.

Figs. 7 and 8 are diagrammatic representations of a coin collector which may be operated by the magnets 103 and 104. The armature 120, shown in Fig. 7 is in its neutral osition and controls fingers 121 and 122 which act to collect coins inserted in the chute 123. When magnet 103 (Fig. 7) is energized as described, the armature 120 rotates in a counter-clockwise direction anal does not move the fingers 121 and 122 but does close the contacts 110 and 111 (Fig. 1') as will hereinafter appear. The'magnet 103 is under certain conditions energized so that its armature will rotate in the opposite direction thus closin contacts 110 and 124 (Fig. 1 and moving the fingers 121 and 122 to the osition shown in Fig. 8. Upon the energization of magnet 103 in this manner if one or more coins have been inserted in the chute 123. then the first will be deposited in the collection chute 125 in the position of coin 126. In this position contacts 127 and 128 will be closed and the coin 126 will hold the next coin 129 in the position shown in Fig. 8 so that upon the deenergization of magnet 103 the coin 126 will be dropped in the till 130, and the coin 129 will be retained in the position shown in Fig. 7.

Thus if a plurality of coins is inserted in the chute 123, one coin will be collected for each complete operation of magnet 103. If there are coins left in the chute 123 at the conclusion of a conversation or if connection has been made to such a line that magnet 103 will be energized to rotate its armature in a counter-clockwise direction, then the energization of magnet 104 upon the replacing of the receiver on its hook will move the finger 131 and allow the coins still left in the chute 123 to move down into the refund chute 132.

Referring to Fig. 1 a substation circuit with a calling device of the type disclosed in the patent to Keith, Erickson and Erickson, No. 1,101,853, is shown. \Vhen the subscriber at substation 101 removes his re ceiver 133 from the receiver hook 134. a circuit is closed from conductor 150, the primary winding of induction coil 135, contact 136, contact 137 which is moved upwardly on the removal of the receiver from its hook, transmitter 138 to line conductor 151, thus extending a low resistance bridge from conductor 150 to conductor 151. The receiver circuit is as follows: from receiver 133, secondary winding of induction coil 135, contact 139, contact 140. condenser 141, transmitter 138, contact 137, contact 136, to receiver 133.

Referring to Fig. 1, there a substation circuit the same in many respects as that shown in Fig. 1 In this case, however, the pair of contacts 142 and is illustrated iii;

143 are included 1n the transmitter cir- 1 147 moving along the under ed e of cam 145 raises it still further until t e insulating stud 148 mounted thereon moves beyond the bent portion of contact spring 142 and allows the connection between contacts 142 and 143 to be opened. When the member 146 returns to its normal position, the cam 145 is retained in its upper position by the insulating stud 148 being hooked over the bent portion of the sprin 142, and thus the connection between springs 142 and 143 is maintained open throughout the conversation. \Vhen the receiver is replaced on its hook at the conclusion of the conversation stud 144 bears against spring 142 in such a manner as to allow cam 145 to return to its normal position. It will be seen therefore that the connection between springs 142 and 143 is opened when the subscriber at substation 102 has removed his receiver and manipulated his dial. In case substation 102 is called, then, since the receiver is removed from its hook but the dial is not manipulated, the connection between springs 142 and 143 is maintained closed. The function of this will appear in connection with the description of the operation of the substation coin collector.

Referring to Fig. 11 the coin collection and refund magnets of a coin collector, such as is used in Fig. 1 are illustrated. The coin collection magnet comprises two coils 900 and 901 and a permanent magnet 902. The armature 903 is placed in operative relation to these coils and held in its neutral osition by means of springs 904 and 905.

he armature 903 is provided with two ins 906 and 907 for controlling the coins. in 906 is securely attached to the armature and is of a length insu'flicient to project into the coin chute 908 so as to interfere with the travel of the coins when the armature is in its.neutral position. Pin 907 is attached to the armature 903, but insulated therefrom. This pin cooperates with a pivoted pin 909 which is of sufiicient length to proect into the coin chute 908 and stop any coins which may be inserted in the said chute. The refund magnet 910 is provided with an armature 911 controlling the pin 912 which also projects under ordinary conditions out into the coin chute and together with the pin 909 holds any deposited coins, such, for instance, as 913 shown in Fig. 13. When a coin thus rests on the two pins 912 and 909, pin 909 is moved toward the right and makes contact with insulated pin 907. Insulated pin 907- is connected through a conducting iece 914 provided with the contact 915 wiiich makes contact with the spring 916 under ordinary conditions. When the armature 903 is moved either in a clockwise or counter-clockwise direction, the connection between spring 916 and contact 915 is broken and the armature 903 is connected to the spring 916 and the spring 916, in turn, 18 connected to the spring 917, as shown in Fi 9 and Fig. 10.

f when the armature 903 is in its neutral position a lurality of coins are inserted in the coin ciute 908, they will assume the position shown in Fig. 13, the first one 913 resting on the pins 912 and 909, and pin 909 making contact with pin 90?. \Vhen the magnets 900 and 901 are energized in the direction to cause the armature 903 to rotate in a counter-clockwise direction, the first coin 913 will dro into the collection chute 918. Since the pm 907 is withdrawn from the path of the coins the second coin 919 will lodge against the pin 906 and be held in position of coin 919 of Fig. 14. When the armature 903 again resumes its neutral position, coin 919 of Fig. 14 will take up the position of coin 913 in Fig. 13. Thus, for each operation of the armature 903, one coin will be collected.

1 If the armature 903 should be rotated in the opposite direction then the coins will remain in the osition shown in Fig. 13, being pushed slightly upward, but no coin will be collected or refunded.

When the refund magnet 910 is operated the pin 912 is withdrawn from the path of the coins and the coins will drop into the refund chute 920 in the manner indicated in Fig. 15.

The manner in which this coin collector is operated will be apparent from the circuit shown in Fig. 1. When the subscriber at station 102 removes his receiver from its hook, the cam 145 will be pushed slightly upward and when he manipulates his dial, the pin 147 ridin on the under surface of cam 145 will push it further upward until the insulating stud 148 allows the spring 142 to break contact with spring 143. When the connection has been established, the transmitter circuit of the callin station will be open at the springs 142 and 143 and the calling subscriber will not be able to converse with the called subscriber until a coin is deposited. When a coin is deposited a connection will be made between contacts 907 and 909 and current will flow from conductor 150, throu h s rin 916, contact 915, conductor 914, pm 90 pm 909, coils 900 and 901 to conductor 151, thereupon the coin collector magnet will be energlzed and will rotate the armature 903 111 a counter-clockwise direction, whereu on the coils 900 and 901 will be locked into an energizing circuit independent of a connection between pins 907 and 909. Such a connection will extend from conductor 150, spring 916, armature 903, coils 900 and 901 to conductor 151. Thereupon a connectlon between springs 916 and 917 will be established which will substitute for the connection between springs 142 and 143, so that the substation 102 will be put into an operative condition. This condition will last until the end of a predetermined interval of time when the conductors 150 and 151 will be short-circuited and the coils 900 and 901 will be deprived of current so that armature 103 will return to its normal position. Thereupon the substation 102 will be disabled until another coin is deposited.

If a plurality of coins are deposited, the collection of coins will take place automatically and the conversational circuit will not be interrupted.

Operation of A switch.

Each calling substation is provided with an individual switch known as an A switch whose function it is to connect the calling line to a first selector or B switch. The A switch is a non-numerical switch having a trunk hunting operation only. The A switches shown in Figs. 1, 1 and 1 are exactly alike and a description of the switch shown in Fig. 1 will apply equally well to Figs. 1 and 1 \Vhen the subscriber removes his receiver from its hook a circuit is established from ground, the normal contact on which brush 162 rests, the back contact and upper armature of relay 157, conductor 150 through the loop of the substation, conductor 151, inner lower armature and back contact of relay 157, brush 163 and its normal contact, winding of relay 158 to battery and ground. Relay 158 is energized in this circuit and extends the ground on its winding through its righthand armature and front contact to the back contact and armature and winding of magnet 160 to battery and ground. Magnet 160 is the motor magnet of this switch and upon its energization moves the brushes 61 to 167, inclusive, forward one step. If the first trunk encountered by these brushes is busy, a ground will be found on terminal 171 which will be extended through brush 164, the left-hand armature and front contact of relay 158, the front contact and right-hand armature of relay 158, winding of relay 158 to battery and ground, thus maintainii g relay 158 energized. This ground will also be extended to the back contact and armature of motor magnet 160 so as to cause it to continue to step. The ground on the front contacts of relay 158 is also extended through brush 166 to terminal segment 173 and thence to the winding of relay 157 which opens the original circuit for relay 158 and prevents the connection of substation 101 through the brushes 162 and 163 to the terminals of busy trunks.

When an idle trunk has been encountered and no ground is found on terminal 171, the original energizing circuit of relay 158 having been opened by the advance of brush 163 from its normal terminal, relay 158,will

become deenergized and open the circuit of motor magnet 160 and cut-off relay 157 whereupon the brushes 161 to 1.67, inclusive, will come to rest on terminals 168 to 174, inclusive, of an idle trunk.

\Vhenever the A switch has been moved from its normal position, the brush 167 moves on to terminal segment 174, thereby connecting ground to conductor 154 to mark this line as busy. conductors 152, 153, 154 leading to the called multiple of this line.

When substation 100 is connected through conductors 152 to 154, inclusive, as a called substation then a ground is placed on a conductor 154 in a manner hereinafter to be described, and this ground is extended through brush 167, its normal contact, wind ing of cut-off relay 157 to battery and ground whereby the connection from conductors 150 and 151 is severed from the brushes 162 and 163.

As will hereinafter appear, magnet 159 is a release magnet and functions to return the A switch to normal, this circuit being closed at the conclusion of a conversation through means hereinafter described.

Operation of B switch.

The calling subscribers line now having been extended by the A switch to a first selector or B switch, the subscriber manipulates his dial to directively set the B switch on to the terminals of a desired trunk line. U on the finding of an idle trunk line to the g switch by the A switch, relay 158 becomes decnergized and a circuit is established from ground, back contact and left-hand armature of relay 158, brush 164, terminal 171, conductor 200, terminal 201, brush 207, winding of cut-01f relay 213 to battery. This relay becomes energized and remains in this condition until the brushes of the B switch come to rest on the terminals of the desired trunk line. The subscriber at substation 100, now manipulates his dial 175 to send a series of impulses. As the dial 175 is set, contacts 108 and 109 are opened and remain in this condition until the dial returns to its normal position. During the return movement of dial 175, line 150 is grounded a number of times, and thereafter line 151 is grounded once. The impulses sent over the line 150 are for the purpose of directively setting the switch in relation to the desired group of trunks, and the single impulse following over line 151 is for the purpose of causing the changeover whereupon the B switch begins to automatically rotate overthe terminals of the desired group of trunks until an idle one is found. Each of the impulses sent over line 150 flows in a circuit from ground, the upper dial spring in dial 175, line 150, upper armature and back contact of relay 157, brush 162, terminal 169, polarized relay 214, upper armature and front contact of relay 213, winding of impulse relay 215 to battery and ground. Relay 215 only responds to each one of these impulses and each time it so responds it establishes a circuit from ground, Inner right-hand armature and back contact of relay 216, right-hand armature and front contact of relay 215, windin of motor magnet 217 to battery and groun Magnet 217 steps brushes 207 to 212, inclusive, over groups of trunks. When these brushes have been set in relation to the proper group of trunks, a single impulse is sent from ground, the lower dial spring of dial 175, conductor 151, inner lower armature and back contact of relay 157, brush 163, contact 170, polarized relay 218, inner lower armature and front contact of relay 213, left-hand windin of relay 216, to battery and ground. A ter the brush 207 had left its normal contact, on the first step caused by the first energization of magnet 217, a circuit is established for maintaining relay 213 energized as follows: from ground, the back contact and outer ri hthand armature of relay 216, winding 0 release relay 219, lowermost armature and front contact of relay 213, terminal segment 220, brush 207, winding of relay 213, to battery and ground. The current flowing in this circuit is sufficient to maintain relay 213 energized but is not sufficient to enerize the release relay 219. lVhen relay 216 15 energized in the circuit described, it attracts its armatures and breaks the circuit for the energization of relay 213, but if the first trunk of the selected group is busy, then a ground will be found on a terminal such as 221 which will be extended through brush 208, the left-hand armature and front contact of relay 216, lowermost armature and front contact of relay 213, terminal segment 220, brush 207, winding of relay 213 to battery and ground, for maintaining relay 213 energized during the ensuing trunk hunting operation. A branch of this circuit will extend fromQthe left-hand armature and front contact of relay 216, through. the winding of release rela 219, the outer right-hand armature and ront contact of relay 216, the right-hand winding of relay 216 to battery and ground to maintain relay 216 energized. This circuit also branches at the outermost right-hand armature and front contact of relay 216 and extends through the back contact, armature and winding of motor magnet 226 to battery and ground. As long as busy trunks are encountered a ground will be extended through brush 208 to maintain relays 213 and 216 energized and to provide an energizing circuit for magnet 226. Magnet 226 in energizing steps the brushes 207 to 212, inclusive, forward and breaks its own circuit whereupon it releases, and becoming energized a ain steps the brushes forward once more. his will continue until an idle trunk is encountered whereupon no ground being extended to brush 208, relays 213 and 216 become deenergized and magnet 226 ceases to operate. As in the first case, these latter circuits throu h the release relay 219 are not of such a character as to cause its energization and the manner in which it is energized to release the switch will be described hereinafter. F or the purpose of this disclosure it will be assumed that the brushes 207 to 212 have been stepped forward in their primary movement by the motor magnet 217 under the direction of the substation dial 175, and automatically under control of motor magnet 226, until an idle trunk connected to terminals 221 to 225, inclusive, has been encountered. 111 will be assumed in this case that this trunk is one which may extend throu h the circuits of Fig. 3 to a circuit whic is known as the H switch. This is not in fact a switch but rather a repeating circuit for the trunk which leads to an ofiice at a distance and is provided as it is necessary to control the switch at the distant olfice over two wires.

The circuit shown in Fig. 3 is identical with that shown in Fig. 3 with the exception that the auxiliary L switch is connected somewhat differently. These two figures represent trunk lines of different character, that is, trunk lines leading to diiferent ofi'ices and therefore of different lengths. In the case of Fig. 3 the L switch is so or anized as to require the payment of two to] charges, and the L switch of Fig. 3 is so organized as to require the payment of three toll charges as will hereinafter be more fully explained.

Operdtiowof H and C Switches.

The calling sidiscriber now manipulates his dial 17 5 1n the same manner as heretofore described. The series of impulses is transmitted over the up or talking c0nductor through polarized relay- 300, the outer left-hand armature and back contact of relay 301, outer left-hand armature and back contact of relay 302, winding of relay 303 to battery and ground. The first impulse of the series energizes relay 303 which thereupon extends a circuit from ground, the front contact and right-hand armature of relay 303, conductor 304, conductor 305, conductor 400, upper armature and back contact of relay 401, brush 405, terminal 409, windin of realy 411, to battery and ground. Re ay 411 completes a circuit from ground, left-hand armature and front contact of relay 411, terminal 406, brush 402, winding of relay 401 to battery and ground. Relay 401 becomes energized in this circuit and substitutes a direct connection from its Inn upper armature and front contact to the winding of rela 411 in place of that heretofore described: At the same time relay 411 completes a circuit from ground, the inner right-hand armature and back contact of relay 412, the right-hand armature and front contact of relay 411, winding of motor magnet 413 to battery and ground. Magnet 413 steps the brushes 402 to 406, in-

clusive, forward whereupon the brush 402 is brought into connection with terminal segment 414, and a circuit is established from ground, back contact and outer ri hthand armature of relay 412, winding release relay 419, outer lower armature and front contact of relay 401, terminal segment 414, brush 402, winding of relay 401 to battery and ground. Thus relay 401 is maintained energized until relay 412 becomes deenergized. Each impulse which energizes relay 303, in turn causes the energization of relay 411 and the energization of motor magnet 413. whereby the brushes 402 to 406, inclusive, are stepped forward into relation with the desired group of trunks.

Just before the substation dial 175 comes to rest, a single impulse is sent over the lower talkin conductor 315 to conductor 306, inner le t-hand armature and back contact of relay 301, inner left-hand armature and back contact of relay 302, winding of relay 307 to battery and ground. Relay 307 establishes a circuit from ground, front contact and right-hand armature of relay 307, conductor 308, conductor 309, winding of polarized relay 420, winding of polarized relay 421, inner lower armature and front contact of relay 401, left-hand winding of relay 412 to battery and ground. Relay412 becomes energize in this circuit and o ens the circuit for relay 401, but if the rush 403 is resting on the terminal of a busy trunk, then as before, a substitute connection for the energization of rela 401 will be provided. Such a circuit wil extend from ground, terminal 415, brush 403, left-hand armature and front contact of relay 412, lowermost armature and front contact of relay 401, terminal segment 414, brush 402, winding of relay 401 to battery and ground. This ground will also be extended from the lefthand armature and front contact of relay 412, through the winding of release relay 419, outer ri ht-hand armature and front contact of re ay 412, the right-hand winding of relay 412 to battery and ground to maintain relay 412 energized. This circuit will be further extended from the outer right-hand armature and front contact of relay 412 to the back contact and armature of magnet 422, winding of magnet 422 to battery and ground whereupon magnet 422 will automatically ste the brushes 402 to 406, inclusive, forwar until an idle trunk is encountered. The'reupon relays 401 and 412 will become deenergized and magnet 422 will cease to operate. Relay 419 will not become energized in any of the circuits just described.

Operation of D Switch.

It will be assumed that the Q switch has been set so that its brushes 402 to 406, inclusive, have come to rest upon terminals 414 to 418, inclusive, of an idle trunk in the desired group and that the circuit is new extended to the D switch of Fig. 5.

Upon the deenergization of relays 412 and 401, a circuit will be established from round, the back contact and outer rightfiand armature of relay 412, the winding of relay 419, the lowermost armature and back contact of relay 401, brush 403, terminal 415, conductor 500, terminal 501, brush 506, winding of relay 511 to battery and ground. Relay 511 becomes energized in this circuit and performs a function similar to relay 401 of the C switch, relay 213 of the B switch, and relay 157 of the A switch in a manner similar to that heretofore described. The calling substation 100 now sends a series of impulses which affect relay 303 which in turn intermittently grounds the upper talking conductor 305 which ground will now be extended over conductor 400, the upper armature and back contact of relay 401, brush 405, terminal 417, upper armature and front contact of relay 511, winding of relay 512 to battery and ground. Relay 512 intermittently establishes a circuit from ground, inner left-hand armature and back contact of relay 513, the lefthand armature and front contact of relay 512, winding of motor magnet 514 to battery and ground. Motor magnet 514 steps the brushes 506 to 510 inclusive, forward into relation with the desired group of trunks. Thereafter a single impulse is sent over the lower talking conductor to energize relay 307 which in turn places a ground for a brief interval on conductor 309 which is thereupon extended through the inner lower armature and back contact of relay 401, brush 404, terminal 416, inner lower armature and front contact of relay 511, lefthand winding of relay 513 to battery and ground. During the stepping of the D switch in its primary direction, and after the brush 506 has left its normal terminal 501, a circuit was maintained for the energization of relay 511 from ground, the back contact and outer right-hand armature of relay 513, winding of relay 515, lowermost armature and front contact of relay 511, terminal segment 516, brush 506, winding of relay 511 to battery and ground. Upon the energization of relay 513 this circuit is broken but a substitute circuit is thereupon established from ground on terminals such as 517 over which the brush 507 now passes in searching for an idle trunk of the selected group: brush 507, outer left-hand armature and front contact of relay 513 lowermost armature and front contact oi relay 511, terminal segment 516, brush 506, winding of relay 511 to battery and ground, This circuit is also extended through the winding of rela 515, the outer right-hand armature and ront contact of relay 513, right-hand winding of relay 513 to battery and ground to maintain rela 513 energized "ntil an idle trunk is foun This circuit is also further extended from the outer ri lit-hand armature and front contact of re ay 513, back contact and armature of motor magnet 521, windin of magnet 521 to battery and ground. This is a self-interrupting magnet and controls the brushes 506 to 510, inclusive, so as to step them forward automatically until an idle trunk is selected. When such an idle trunk has been encountered it will be denoted by the absence of ground on the terminals such as 517 whereupon relays 511 and 513 will become deenergized and magnet 521 will cease to operate. The D switch is now set upon the terminals of an idle trunk in the desired group and a G switch or final connector has been selected. The complete circuits of this switch are shown in Fig. 6 and diagrammatically in Figs. 16 and 16, the difference between the two being that one isconnected as an ordinary connector switch, and the other is arranged as a connector switch serving the free or reverse service lines. Fig. 16 represents a connector of the first type and Fig. 16 represents a connector of the last type. We will assume at this time that the connection has been established to an ordinary connector switch.

Operation of 6' switch.

A circuit is now established from ground, back contact and outer ri ht-hand armature of relay 513, winding of re ay 515, lowermost armature and back contact of relay 511, brush 507, terminal 517, conductor 600, terminal 601, brush 607, winding of relay 613 to battery and ground. Relay 613 becomes energized in this circuit and attracts its armaturcs in the manner and for the same purpose heretofore described in connection with similar relays in the A, B, (1" and *D" switches. The calling subscriber now sends his last series of impulses to set the G switch on the terminals of the called line. This series of impulses is relayed by relay 303 so that ground is extended to conductor 614, conductor 627, back contact and outer left-hand armature of relay 618, winding of relay 616, to battery and ground. Relay 616 therefore responds to the intpulses now being sent by the calling substation. Upon each attraction of its armatures by relay 616, a circuit is established from ground, right-hand armature and front contact of relay 616, winding of motor magnet 619, front contact and inner upper armature of relay 613, back contact and lefthand armature of relay 617 to battery and ground. Magnet 619 steps the brushes 607 to 612. inclusive, forward on to terminals 620 to 625, inclusive, of the called line. After the brush 607 has left its normal position, a circuit for relay 613 is maintained over a path from ground, back contact and inner right-hand armature of relay 617, inner lower armature and front contact of relay 613, terminal segment 620, brush 607, winding of relay 613, to battery and ground. Following the series of impulses which actuates relay 616, a single impulse is transmitted over the lower talking conductor which is relayed by relay 307 of the H switch and thence to conductor 626, winding of relay 617, inner right-hand armature and back contact of relay 618. to battery and ground. Relay 617 responds to this single impulse and opens the circuit for the energization of relay 613, just described.

(ailed Zine busy.

If the called line is busy, terminal 621 will be grounded and this ground will be extended over brush 608, front contact and inner right-hand armature of relay 617, inner lower armature and front contact of relay 613, terminal segment 620, brush 607, winding of relay 613 to battery and ground whereby relay 613 is maintained in its energized position. A circuit is now alternately closed and opened from ground throu h the ringing current interrupter 628, secon ary winding of busy tone transformer 630, terminal segment 624, brush 611, outer ri lit-hand armature and back contact of re ay 618, front contact and outer upper armature of relay 613, condenser 629, conductor 614, conductor 627, biKl. contact and outer left-hand armature of relay 618, relay 616, to battery and ground. No direct current flows through this circuit on account of the condenser 629 but since the secondary winding of the busy tone transformer 630 is included in the circuit just described, busy tone will be transmitted by induction to the calling subscrihers receiver whereby he will be notified that the called line is busy.

Release of connection.

If the calling subscriber replaces his receiver on its book he thereby simultaneously grounds both conductors 150 and 151, through the winding of magnet 104. Magnet 104 is energized in this circuit and removes the finger 131 so as to allow any coins inserted in the chute 123 to fall down into the refund chute 132. In series with the magnet 104 and in parallel with each other Hit! in this circuit are relays 303 and 307. These relays will thereupon simultaneously connect ground to conductors 305 and 309, resulting in the simultaneous energization of relays 616 and 617. Thereupon a circuit is established from battery, the left-hand armature and front contact of relay 617 the left-hand armature and front contact of relay 616, winding of release relay 631, conductor 600, terminal 517, brush 507, back contact and outer lower armature of relay 511, winding of relay 51-5, outer right-hand armature andback contact ,of relay 513 to ground. Thus, relays 631 and 515 are included serially in a circuit. In such a circuit both of these relays become energized. Relay 631 attracting its armature establishes a circuit from ground, the right-hand armature and front contact of relay 631, armature and back contact of relay 632, windin of release magnet 633 to battery and groumf Relay 633 becomes energized and returns brushes 607 to 612 to their normal position. In a similar manner relay 515 becomes energized and establishes a circuit from ground, back contact and outer, right-hand armature of relay 412, winding of. relay 419 outer lower armature and back contact of relay 401, brush 403, terminal 415, conductor 500, armature and front contact of relay 515, winding of release magnet 522. to battery and ground. Thus relay 419 and magnet 522 are serially included in the same circuit and in this circuit they both become energized. Magnet 522 causes the brushes '506 to 510. inclusive, to return to their normal positions.

Relay 419 becoming energized establishes a circuit from ground, right-hand armature and front contact of relay 419, winding of release magnet 423 to battery and ground. Magnet 423 causes brushes 402 to 406, inclusive, to be returned to their normal positions.

In the meantime, relays 303 and 307 which were simultaneous] energized complete a circuit from groun back contact and outer rifght-hand armature of relay 216, winding 0 relay 219, outer lower armature and back contact of relay 213, brush 208, terminal 221, conductor 310, left-hand armature and front contact of relay 303, front contact and lefthand armature of relay 307, winding of relay 311 to battery and ground. Relays 311 and 219 being included serially in the same circuit, both become energized. Relay 311 places ground on each of the conductors 305 and 309 to insure the release of the C, D and G switches.

Relay 219 attracting its armature establishes a circuit from ground, right-hand armature and front contact of relay 219, winding of release magnet 245, to battery and ground. Magnet 245 becomes energized in this circuit an causes the brushes 207 to relay 157, to battery and ground. Magnet,

159 becomes energized in this circuit and causes the brushes 161 and 167, inclusive, to be returned to their normal positions. Thus, the entire connection is restored.

Ualled line idle.

Assuming on the other hand that no ground is found on terminal 621, thus denoting that the called line is idle, the circuit for relay 613 having been broken at the inner righbhand armature of relay 617 and no substitute circuit provided, relay 613 therefore becomes deenergized. A circuit is now established from ground, current interrupter 628, secondary winding of busy tone transformer 630, terminal segment 624, brush 611, outer right-hand armature and back contact of relay 618, winding of relay 634, back contact and left-hand armature of relay 635, back contact and inner u per armature of relay 613, back contact and efthand armature of relay 617 to battery and ground. Relay 634 is thereupon intermittently energized according as the circuit is intermittently closed through the interrupter 628. Upon each energization of the relay 634, a circuit is closed from a source of ringing current 636, front contact and lower armature of relay 634, brush 609, terminal 622, condenser 680, contact 681, contact 682, ringer 683 to ground. Thus the ringer of the called subscribers line is alternately rung and this will continue until the subscriber at station 650 responds by taking his receiver 06' from its book. Thereupon a low resistance bridge is thrown across conductors 652 and 653, and when the interrupter 628 has come to an open position and relay 634 is deenergized, a circuit is established from ground, back contact and inner right-hand armature of relay 617 winding of relay 632, outer upper armature and back contact of relay 613, back contact and outer right-hand armature of relay 617, back contact and upper armature of relay 634, brush 610, terminal 623, conductor 652, low resistance bridge of the substation, conductor 653, terminal 622, brush 609, lower armature and back contact of relay 634, back contact and outer lower armature of relay 613, winding of relay 618 to battery and ground. Relays 632 and 618 become energized in this circuit. Relay 632 in attractm its armature opens the circuit for the refiaase magnet 633, so that even should the calling subscriber now hang up his receiver, the G switch will not be returned to nor- Ill 

